Question 1

Most three-phase, dry-type distribution transformers are connected as a primary wye connection.

Accepted Answer

False

Question 2

Three-phase transformers should have a voltage ____________________ to show the angular phase displacement between the primary and the secondary and also the phase-sequence order.

Accepted Answer

vector diagram

Question 3

In three-phase transformers, the ____________________ or phase sequence between the primary and the secondary is critical.

Accepted Answer

phase rotation

Question 4

If the pattern is a delta-delta pattern, the displacement must be 60°.

Accepted Answer

In a delta-delta transformer connection, the phase displacement between the primary and secondary sides is 0 degrees, not 60 degrees.

Question 5

What is the only way to change the angular displacement?

Accepted Answer

The answer of What is the only way to change...

Question 6

N is the ____________________ in the vector diagram.

Accepted Answer

The answer of N is the ____________________ in the vector...

Question 7

It is only necessary to connect the similarly marked high- and low-voltage terminals if the transformers have the same voltage ratio, the same percent impedance, and the same angular displacement.

Accepted Answer

Connecting the similarly marked high- and low-voltage terminals is only necessary if the transformers have the same characteristics of voltage ratio, percent impedance, and angular displacement. Otherwise, it may result in incorrect phase shifts and damage to the transformers.

Question 8

How are the three high-voltage and secondary leads marked?

Accepted Answer

The answer of How are the three high-voltage and secondary...

Question 9

If the transformers are delta-wye or wye-delta, the angular displacement is ____________________°.

Accepted Answer

The answer of If the transformers are delta-wye or wye-delta,...

Question 10

What are the advantages of paralleling three-phase transformers?

Accepted Answer

The answer of What are the advantages of paralleling three-phase...

Question 11

Terminal markings indicate all the relationships between primary and secondary.

Accepted Answer

Terminal markings on transformers indicate connections and polarity but do not detail all the relationships between primary and secondary windings, such as impedance, voltage ratio, or phase shift.

Question 12

How does the American National Standards Institute (ANSI) define the angular displacement?

Accepted Answer

The answer of How does the American National Standards Institute...

Question 13

All phase windings within the transformer normally have the same relative polarity.

Accepted Answer

This is because all phase windings are wound in the same direction and connected properly in a delta or wye configuration, resulting in the same relative polarity.

Question 14

When paralleling three phase transformer units, only transformers with the same ____________________ should be connected.

Accepted Answer

The answer of When paralleling three phase transformer units, only...

Question 15

What is the disadvantage of paralleling three-phase transformers?

Accepted Answer

The answer of What is the disadvantage of paralleling three-phase...

Quiz 21: Three-Phase Transformers, Power Relaying, and Monitoring